1. Field of the Invention
Embodiments of the present invention relate generally to a system and method for encoding a computer rendered image sequence for communication across a network to a remote display. Specifically, progressive refinement techniques are utilized to refine visually persistent static image portions of the computer rendered image sequence. When a visually persistent image portion undergoes motion (e.g., scrolling of an image) before image refinement is complete, lossless motion vectors convey the movement of the partially refined image portions. Once motion stops, image portions are reconstructed using quality attributes of the partially refined image portions prior to the motion.
2. Description of the Related Art
Progressive Image Transmission (PIT) methods are currently used for the communication of large media data sets, such as photographs or video, over limited bandwidth communication channels. Related image refinement techniques, such as Advanced Video Coding (AVC) extensions to standards like H.264/MPEG or Fine Grain Scalability (FGS) methods, provide sub-stream information which enables increased quality of reconstructed remote images if sufficient bandwidth is available.
While PIT methods are aimed at intra-frame compression, motion compensation methods known to the art take advantage of inter-frame attributes of an image stream to increase compression. For example, block motion compensation is a technique in which blocks in a partitioned frame are predicted from blocks of equal size in a reference frame. The blocks are not transformed in any way apart from being represented by a motion vector describing the shifted position of the predicted block. In Motion Photographic Experts Group (MPEG), blocks within frames are predicted using motion compensation, and error (residual) data is then compressed using transform encoding and transmitted. In regard to remote computing applications, some remote display technologies, such as the Stateless Low-Level Interface Machine (SLIM), use vectors in the form of copy commands to copy select areas of a remote display image from one region of the remote display to another rather than re-communicating the relocated image data. Such methods require large amounts of network bandwidth to communicate the original image content to the remote display before such copy commands can be invoked, adding latency to a user's interactive experience at a remote display when the original image is subjected to motion.
Therefore, there is a need in the art for efficiently communicating a dynamic computer display image representation from a host computer to a remote computer display.